On Fri, Jan 4, 2019 at 7:06 AM John Clark <johnkcl...@gmail.com> wrote:

> On Thu, Jan 3, 2019 at 3:58 AM Bruce Kellett <bhkellet...@gmail.com>
> wrote:
>
>
>> *> The 't' in your formula above is the coordinate time, not the proper
>> time. *
>>
>
> What the hell are you talking about? If I travel from event A to event B
> and use the formula x^2 + y^2 + z^2 -(ct)^2  where x,y,and z are the
> differences in spatial coordinates I observe and *t is the proper time*
> it took for me to make the trip I will get an invariant.  If you also
> travel between event A and B but use a different path you will get entirely
> different numbers for x, y and z and you will get a different number for *the
> proper time t,* but when you plug in your numbers into x^2 + y^2 + z^2
> -(ct)^2  you will get the exact same value I do.
>

You clearly do not know =what 'proper time' is.


>
>
>> *> The proper time is defined as the time kept by a perfect clock
>> travelling on a geodesic.*
>>
>
> No it is not! The  proper time is defined as the time measured by a clock
> along ANY line through spacetime and it doesn't matter a hoot in hell if
> that line is a geodesic or not. And you said "*Proper time is the
> distance through spacetime*" but every book on physics on the planet will
> tell you that the distance through spacetime is an invariant; but proper
> time is NOT a invariant,
>

Wikipedia thinks that it is.....at least in non-curved space-times.


> different observers can have different proper times, even you know this
> because you said "*two different orbits of the Earth, both geodesics, can
> coincide at a pair of events.  They will measure different proper times
> between those events*". So your ideas are not self consistent but then
> they had to be, spacetime distance and proper time aren't even in the same
> units.
>
> The reason you need both a odometer and a clock in your car is that they
> measure different things. And no matter how hard you try you're never going
> to be able to subtract seconds from meters, so why are we still arguing
> about this when it's obvious you're wrong?
>

Have you never heard of natural units, units in which c = 1?

Bruce


> > *And a geodesic is the path along which the rate of time is constant.*
>>
>
> What the hell?! Obviously the rate of time is always constant for any
> observer in the same reference frame as the clock regardless if the path is
> a geodesic or not, it will always change at the rate of one second per
> second . It doesn't take a Einstein to know that.
>
> John K Clark
>

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